Profiled protective tape for rotor blades of wind turbine generators

ABSTRACT

A multilayer protective tape for rotor blades of wind energy turbines is provided herein. The protective tape comprising a protective top layer comprising a polymer film, and an adhesive bottom layer. The top layer having a continuous surface (S) that is outwardly curved or outwardly trapezoidal such that the tape has a cross-sectional profile having an inner section between first and second edge lateral sections. The inner section comprises up to 30% of the width of the tape and has a thickness (Ti), while the first and second edge lateral sections have a thickness of T1 and T2, respectively, wherein Ti greater than each of T1 or T2, and the thickness (T1 or T2) of at least one edged lateral section is at most 600 μm and the thickness of the inner section (Ti) is at least 330 μm. 
     Also provided is a method for applying the tape to rotor blades and a rotor blade protected by said protective tape.

CROSS REFERENCE TO RELATED APPLICATIONS

This application a continuation of U.S. patent application Ser. No.15/630,192, filed Jun. 22, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/235,542, filed Jan. 29, 2014 (now U.S. Pat. No.9,718,992), which is a national stage filing under 35 U.S.C. 371 ofPCT/US2012/048219, filed Jul. 26, 2012, which claims priority toEuropean Patent Application No. 11176051.8, filed Jul. 29, 2011. Thedisclosures of all applications mentioned above are incorporated byreference in their entirety herein.

FIELD

The present disclosure relates to a protective tape for a rotor blade ofa wind turbine generator. The tape has a non-uniform thickness profilein a widthwise direction.

BACKGROUND

Rotor blades of wind energy power plants are made of compositematerials, typically glass-fiber composites. The materials can bedamaged by rain, sand, ice, and hailstones, a process which is commonlyreferred to as “erosion”. Protective tapes can be applied to the rotorblades to protect them from erosion. Typically, the tapes are wrappedaround the leading edge of the rotor blade and adhered to the blade byan adhesive. Commercial tapes are usually planar and comprise a polymerfilm as protective layer and an adhesive layer for attachment to therotor blade. Typical tapes are up to 400 μm thick of which the adhesivelayer typically has a thickness of less than 100 μm to avoid making animpact on the aerodynamic profile of the blade. The tapes may beprepared by extruding the protective resin through a rectangular die ofthe required dimension to define thickness and width of the tape andcoating the adhesive onto the extruded film. The adhesive layer istypically covered on its external surface by a release liner and thetapes are wound up into rolls for storage and handling.

Rotor blade manufacturers apply the protective tapes after removal ofthe release liner to the rotor blade. After application of the tape therotor blades are transported to the wind farms where they are installed.The tapes may also be applied to the blades after they had beeninstalled in the wind farm.

Rotor blades for wind turbine generators are becoming increasinglylonger and typically may now have a span of greater than 40 m, e.g. 60m. Furthermore, wind turbine generators are increasingly set upoff-shore subjecting the protective tape to greater forces and harshererosion conditions. This means that protective tapes have to facestronger forces, for example during transportation to the off-shorepower plant and/or to harsher erosion conditions.

Therefore, there is a need to provide alternative protective tapes thatmay appropriately meet the above described challenges.

SUMMARY

In a first embodiment, an exemplary multilayer protective tape for rotorblades of wind energy turbines is provided here in. The multilayerprotective tape comprising a protective top layer comprising a polymerfilm, and an adhesive bottom layer, wherein the top layer has acontinuous surface (S) that is outwardly curved or outwardly trapezoidalsuch that the tape has a cross-sectional profile having an inner sectionbetween a first edge lateral section and a second edge lateral section.The inner section of said tape comprising up to 30% of the width of thetape, wherein the inner section has a thickness (Ti), while thethickness of the first edge lateral section is T1, and the thickness ofthe second edge lateral section is T2. In this exemplary embodiment, Tiis greater than each of T1 or T2, and the thickness (T1 or T2) of atleast one edged lateral section is at most 600 μm and the thickness ofthe inner section (Ti) is at least 330 μm.

In a second embodiment, a rotor blade of a wind turbine is protectedfrom erosion. The rotor blade comprises a leading edge thatpredominantly faces the wind, a trailing edge opposite the leading edge;and a protective top layer covering and bonded to the leading edge ofthe rotor blade by an adhesive bottom layer. The top layer has acontinuous surface (S) that is outwardly curved or outwardly trapezoidaland wherein wherein the protective top layer and the adhesive bottomlayer have a cross-sectional profile having an inner section between afirst edge lateral section and a second edge lateral section, whereinthe inner section comprises up to 90% of the width of the top protectivelayer. The inner section has a thickness (Ti), the thickness of thefirst edge lateral section is T1, and the thickness of the second edgelateral section is T2, wherein Ti is greater than each of T1 or T2, andwherein the thickness (T1 or T2) of at least one edged lateral sectionis at most 600 μm and the thickness of the inner section (Ti) is atleast 330 μm.

In a third embodiment a method protecting a rotor blade of a windturbine from erosion is provided. The method comprises providing aprotective tape, wherein the protective tape comprises a protectivepolymer film top layer and an adhesive bottom layer having an uppersurface facing the top layer and a bottom surface opposite thereto,wherein the bottom surface is patterned to comprise a plurality ofgrooves or dots, wherein the tape has a cross-sectional profilecomprising an inner section having a thickness Ti between a first edgelateral section and a second edge lateral section, wherein the thicknessof the first edge lateral section is T1, and the thickness of the secondedge lateral section is T2, wherein Ti is greater than each of T1 or T2,wherein the thickness (T1 or T2) of at least one edge lateral section isat most 600 μm and the thickness of the inner section (Ti) is at least330 μm, applying a liquid adhesive to the rotor blade, to the patternedbottom surface of the tape or both, and attaching the tape to a leadingedge of the rotor blade such that the edge lateral sections of the tapeface a trailing edge of the blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings.

FIG. 1A is a schematic perspective representation of a protective tapeaccording to the present disclosure round up to a roll.

FIG. 1B is an enlarged cross-sectional representation of a section ofthe protective tape of FIG. 1A.

FIG. 2A is a schematic cross-sectional representation of the protectivetape according to the present disclosure having a trapezoidal surface.

FIG. 2B is a schematic cross-sectional representation of the protectivetape according to the present disclosure having a trapezoidal surface.

FIG. 3 is a schematic cross-sectional representation of an embodiment ofthe protective tape according to the present disclosure having apatterned adhesive layer.

FIG. 4 is a schematic representation of wet-in-wet coating process ofexample 1.

FIG. 5A is a schematic cross-sectional representation of the profiledrecess of the downstream coating knife used in example 1.

FIG. 5B is the cross-sectional profile of the tape produced in example1.

FIG. 6 is a perspective cross-sectional schematic view of a rotor bladefor wind turbines.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosure,one or more examples of which are illustrated in the drawings. Featuresillustrated or described as part of one embodiment can be used withother embodiments to yield still a third embodiment. It is intended thatthe present disclosure include these and other modifications andvariations.

Protective Tape:

A perspective view of an exemplary protective tape having across-sectional profile according to the present disclosure isillustrated in FIG. 1A, which shows the tape wound up to a roll. Theprotective tape (1) has a length (L), a width (W) and a thickness (T).The length of the tape is its longest dimension followed by its width,wherein the length of the tape is always greater than its width. Thewidth of the tape is always greater than its thickness. Typically, thetape has a width of at least 150 mm. Typically, the tape has a length ofat least 50 cm.

The tape (1) has a profiled cross-section. The surface (S) of the tapehas a cross-sectional profile such that the tape, across its width, hasan inner part between two lateral parts wherein the inner part has athickness (Ti) and the lateral parts have a thickness T1 and T2. Thethickness of the inner part (Ti) is greater than the thickness of atleast one, preferably both lateral parts (T1, T2) of the tape. Thethickness at the inner section of the tape (Ti) may be the maximumthickness of the tape. The surface (S) of the tape is shaped to providethe cross-sectional profile described above. The surface (S) may beoutwardly curved, for example to describe a convex shape (as representedin FIGS. 1A and 1B) or it may be angled to describe a trapezoidal shape(as represented in FIGS. 2A and 2B). Therefore, the tape has a thicknessat its inner section (across its width or cross-section) that is greaterthan at its lateral sections or its edges.

FIG. 1 B shows the layered-construction of the tape (1). The tape (1)comprises a protective top layer (2) and an adhesive bottom layer (3).The adhesive bottom layer (3) contains the adhesive for attachment tothe rotor blade. The top layer (2) and the adhesive bottom layer (3) arearranged parallel to each other. The adhesive layer (3) may contact thetop layer (2) directly, in which case top layer (2) and adhesive layer(3) are superimposed or abutting layers or they may be separated fromeach other by one or more intermediate layers, which are not shown inFIG. 1B. In a preferred embodiment of the present disclosure, the tapedoes not contain intermediate layers between top layer and adhesivelayers, i.e. the top layer abuts the adhesive layer.

The adhesive layer (3) has an internal surface facing the top layer (2)and opposite thereto an external surface. The external surface of thebottom layer faces the rotor blade when applied to the blade. Prior toapplication to the blade, for example, during manufacturing, storage andtransportation of the tape the external surface of the adhesive layer(3) may be covered by a release liner (4).

The surface (S) is typically made up by the top layer (2) of the tape,i.e. the surface of the tape is typically also the surface of the toplayer (2). The top layer (2) has an outwardly profiled surface (S) suchthat the tape has a thickness at its inner part (Ti) that is greaterthan its thickness at its lateral parts (T1, T2) as shown in FIG. 1B.

The thickness at its inner part (Ti) may be greater than 350 μm orgreater than 400 μm and preferably is greater than 500 μm. The tape mayhave a thickness at its inner part of up to 5,000 μm, or up to 2,000 μmor up to 1,000 μm, or up to 745 μm. The inner thickness Ti and thelateral thicknesses T1, T2 are understood to be the sum of therespective thicknesses of the top layer (2) and the adhesive layer (3)which includes the thickness of any intermediate layer(s) between thembut excludes the thickness of any release liner if present. The innerpart of the cross-section of the tape may extend to more than 30%, morethan 50% or even more than 90% or more than 95% or even more than 99% ofthe width of the tape but is less than 100% of its width.

The lateral parts of the tape (1) may have a thickness T1, T2 of at most600 μm, or up to 590 μm, or less than 450 μm, less than 400 μm or lessthan 300 μm, provided the thickness at the inner part (Ti) is greaterthan the thickness of at least one, preferably both lateral parts (oredges) of the tape (1).

Typically the tape (1) has a cross-sectional profile such that it has athickness of at least one at its lateral parts (T1 or T2), preferably atboth of its lateral parts (T1 and T2) of up to 600 μm and an increasingthickness towards its inner part from its lateral parts to reach athickness of greater than 700 μm, greater than 1,000 μm, or 2,000 μm orgreater, or up to 5,000 μm. Typically the thickness increases,preferably continuously, from the lateral parts of the tape towards thecentral part of the tape to reach a maximum thickness of up to about5,000 μm, up to about 2,125 μm, up to about 1,200 μm or up to about1,090 μm. Again these thickness ranges are understood to comprise thethickness of top (2) and adhesive layer (3) including the thickness ofoptional intermediate layers but excluding the thickness of releaseliners (4) if present.

The thickness profile of the tape (1) increases in thickness from thelateral edges towards the inner part to reach a maximum. Such a profilecan be generated by a curved or angular surface (S), which in case ofthe tape (1) represented in FIG. 1A and FIG. 1B is an outwardly curvedsurface. “Outwardly” as used herein above and below means a directionacross the thickness of the tape starting from the adhesive bottom layertowards the top layer, i.e. in the direction towards the weather exposedpart of the tape. Preferably, the increase in thickness is continuous,for example by an outwardly curved shape (as represented in FIG. 1A andFIG. 1B) or a shape having angular sides (as represented in FIG. 2A andFIG. 2B). The maximum thickness may be the apex of a curve or it may bea plateau. The cross-sectional profile may be symmetric. It may also benon symmetric, i.e. the increase in thickness from one lateral parttowards the inner part may be greater than the increase of the otherside. Alternatively, the thickness at the lateral sides of the tape,i.e. T1 or T2 may not be equal. For example, T1 may be greater than T2.The maximum thickness may be in the middle of the tape (across itswidth) or offset from it.

The cross-sectional profile of the tape (1) is continuous. This meansthe profile is not interrupted by a pattern of gaps and grooves.Preferably, the entire surface of the tape (in widthwise and lengthwisedirection) is continuous. The external surface of the tape preferably issmooth. However, it is to be understood that some unevenness may bepresent due to manufacturing constraints, i.e. the surface may have asurface roughness. Generally the surface has a surface roughness (Rz),(DIN EN ISO 4287), of equal or less than 150 μm, preferably, equal orless than 100 μm.

Top Layer:

The top layer (2) contains a polymer film. The polymer typically is athermoplast or an elastomeric thermoplast. The polymer may becross-linked or not-cross-linked. The top layer (2) is typically anextruded polymer film but may also be a coated polymer layer. Polymersthat can be used to make the top layer (2) or that form the top layer(2) include polyurethanes, polycarbonates, fluoropolymers,epoxy-polymers, silicones, polester, polyether, and combinations thereofand co-polymers or graft-polymers thereof. Preferably, the top layer (2)contains a polyurethane (PU) polymer which may be a polyurethane homo-orcopolymer, more preferably, an extruded polyurethane polymer. Theextruded polyurethane may be a thermoplastic elastomeric polyurethane.Thermoplastic elastomeric polyurethanes are known in the art under theabbreviation “TPU”. TPU's are formed by the reaction of: diisocyanateswith short-chain diols (so-called chain extenders) and diisocyanateswith long-chain bifunctional diols (known as polyols). TPU's arecommercially available, for example, under the trade designationsDESMOPAN, TEXIN, UTECHLLAN from Bayer AG, Germany. TPU tapes are alsocommercially available from 3M Company, St. Paul, USA. The polymer filmmay contain additives to improve the performance of the polymercomposition, for example, but not limited to, anti-oxidation agents,UV-stabilizer, processing additives, fillers and the like.

In one embodiment the top layer (2) has a profiled surface (S) asdescribed above but is itself of uniform thickness. This embodiment isrepresented in FIG. 2B, showing a trapezoidal top layer (2) over aprofiled (trapezoidal) adhesive layer (3) on a release liner (4). Suchtape constructions can be obtained by providing an adhesive layer (3)that is already profiled and has a cross-sectional profile as describedabove and onto which the top layer (2) is adhered. Adhesion between thetop layer (2) and the profiled adhesive layer (3) beneath it forces thetop layer (2) to take up the profile of the pre-shaped adhesive layer(3). The top layer of this embodiment preferably has a thickness of atleast 50 μm and up to 1,500 μm or from at least 100 μm up to about 500μm.

A profiled adhesive layer (3) may be generated by feeding a curableadhesive precursor through a coating knife having an appropriatelyshaped recess to create the desired profile and feeding the top layer,preferably provided as a flexible film between the curable adhesivearound the profiled recess of the coating knife and curing the adhesive.

Instead of providing the top layer material as a film it is alsocontemplated by this disclosure to provide the top layer material as acurable polymer composition which can be cured to form a non-adhesivecross-linked polymer and feeding it around the profiled knife and curingthe adhesive precursor and simultaneously or subsequently curing thepolymer material to form the multi-layer tape (1). Suitable curablepolymer compositions include those that are not adhesive after curingand include but are not limited to epoxy compositions, polyurethanecompositions or combinations thereof.

In another embodiment the top layer (2) is of non-uniform thickness,i.e. it has a greater thickness at its inner section than at its lateralsections. This embodiment is represented in FIG. 1B for tapes having aconvex shape and in FIG. 2A for tapes having a trapezoidal shape. Thetop layer (2) of such embodiment may have a thickness at its lateralsections of not more than 400 μm, or not more than 300 μm, or not morethan 200 μm. The top layer (2) has a thickness at its inner part (acrossits width) of more than 550 μm, or at least 610 μm or at least 1.520 μm.The maximum thickness of the top layer (2) may be up to 5,000 μm or upto 1,600 μm. In this embodiment the cross-sectional profile of the tape(1) is generated by the shape of the top layer (2). Tapes according tothis embodiment may be made, for example, by extruding the material formaking up the top layer of the tape through appropriately shaped(profiled) dies and attaching the extruded top layer onto the adhesivelayer by coating, laminating or other techniques known in the art, or bythe wet-in-wet coating process described herein using appropriatelyshaped coating knives with appropriate gaps between knife and substrate.

The top layer (2) of the protective tapes (1) may have a flat continuousinternal surface (i.e., the surface facing the adhesive layer (3)) butmay also have a non flat and/or non continuous surface, for example apatterned internal surface.

Adhesive Layer:

The adhesive layer (3) of the tapes (1) according to the presentdisclosure may be made of known adhesive materials. Preferably, theadhesive is a pressure sensitive adhesive (PSA). Pressure sensitiveadhesives can be applied to a surface using manual force, which issufficient to bond the adhesive to the surface. PSA's may not requiresetting (i.e. hardening through solvent evaporation), chemical orthermal treatment for adhering the adhesive to the substrate. Suitableadhesive materials, in particular but not limited to pressure sensitiveadhesive materials, include, for example, acrylic based adhesives, vinylether based adhesives, natural or synthetic rubber-based adhesives, poly(alpha-olefins) based adhesives and silicone based adhesives andcombinations thereof, which are all known in the art. Specific examplesare disclosed in U.S. Pat. Nos. 4,925,671, 4,693,776, 3,930,102,4,599,265, 5,116,676, 6,045,922, and 6,048,431. The adhesives may beobtained by curing from curable adhesive precursors. This means theadhesives obtain their adhesive properties by curing them, for exampleby a thermal curing reaction, or by irradiation curing, e.g. by actinicirradiation, gamma- or UV-irradiation or e-beam treatment. An example ofUV-curable adhesive precursors includes acrylic adhesives precursors.Those precursors are typically liquid materials which harden or solidifyor at least increase in viscosity upon cross-linking (curing), whichtypically involves UV curing.

The adhesive bottom layer (3) of the present disclosure may also containnon-pressure sensitive adhesive materials. Examples of such materialsare described in U.S. Pat. No. 5,851,664 and WO 99/50902. In addition,the adhesive layer of the present invention may be a non tacky adhesiveas described in U.S. Pat. No. 5,316,846.

Typically, the adhesives of adhesive bottom layer (3) may have aviscosity of at least 2,000, or at least 10,000 or from about 18,000 toabout 60,000 mPas or greater that 60,000 mPas at room temperature.

In particular embodiments the adhesives may be used in combination withsettable adhesives or curable liquid adhesives as will be described ingreater detail below.

Preferably, the adhesive bottom layer (3) comprises at least oneacrylic-based adhesive.

The adhesive materials used in the adhesive bottom layer (3) may alsoinclude additives. Such additives may include, for example, pigments,dyes, plasticizers, tackifiers, rheology modifiers, fillers,stabilizers, UV radiation absorbers, antioxidants, processing oils, andthe like. The amount of additive(s) used can vary from 0.1 to 50 weightpercent of the adhesive material, depending on the end use desired. Theadhesive layer may also contain particles, in particular hollowparticles or agents that expand upon exposure to heat (e.g. blowingagents) to generate a foam adhesive. Also a combination a differentadhesives can be used to combine them into a single adhesive mixture.The adhesive bottom layers (3) provided herein may contain a singleadhesive layer or two or more than two adhesive layers, preferablysuperimposed or abutting layers across its thickness. In a preferredembodiment, the tape (1) contains an adhesive layer (3) containing atleast two abutting adhesive layers and one of them being a foam adhesivelayer. A foam adhesive comprises adhesives containing solid or hollowparticles, like but not limited to solid or hollow glass particles orhollow organic polymer particles, gas-filled (other than air) particlesor air- or gas-filled cavities. Preferably, the foam adhesive layer isplaced underneath the top layer (2), preferably abutting the top layer(2). Foam adhesives may increase the elasticity of the tape which may bebeneficial to the impact dampening properties of the tape.

The adhesive bottom layer (3) may typically have a thickness of fromabout 20 to 120 μm at its lateral sections. In case of a flat, i.e.non-profiled adhesive bottom layer (3) the thickness at its lateralsides is the same as at its inner section. In case of a profiledadhesive bottom layer (3) the bottom layer may have a thickness at itsinner part of at 120 μm or at least 400 μm.

Adhesive Layers with Patterned External Surface

In particular embodiments, the adhesive bottom layer (3) may have apatterned external surface. An embodiment of this type is represented inFIG. 3. The external surface of the adhesive bottom layer (3) is thesurface that faces the rotor blade (when applied to the blade). Forexample, the adhesive bottom layer (3) may contain at its externalsurface a pattern of grooves as shown for the adhesive bottom layer (3)in FIG. 3. In the embodiment represented in FIG. 3 the adhesive bottomlayer (3) is also shaped to generate the profiled surface of the toplayer (2) of the tape (1) but is to be understood that this embodimentcan have any top layer (2) as described herein and a non-profiledadhesive layer. The grooves may extend over the entire width and/orlength of the external surface of the adhesive layer (3) or only overparts or separated sections of it. Preferably the pattern is such thatthe grooves allow an uninterrupted path for a liquid to travel acrossthe width of the tape. The pattern may be symmetric or non-symmetric.The grooves may be parallel to each other or they may be interconnectedwith each other. The grooves may be linear or non-linear. Instead ofgrooves also a dotted pattern, preferably a dotted patterninterconnected by grooves may be used. The grooves may have a width offrom about 5 μm to 5,000 μm (in case of dots the diameter replaces thewidth). They may have a depth of from about 5 μm to 500 μm and in factpenetrate the entire thickness of the adhesive layer, exposing the toplayer (2) or intermediate layer(s) underneath it—if present. In oneembodiment the grooves have a depth that is equal to the thickness ofthe adhesive bottom layer (3). In another embodiment, the grooves have adepth that is less than the thickness of the adhesive bottom layer (3).

The grooves or dots may cover from 20 to 80% of the surface of theadhesive bottom layer (3).

An advantage of a patterned external surface of the adhesive is that itallows the tape to be easier repositioned and/or to be applied withoutentrapping air-bubbles. Another advantage is that such a tape may beused in combination with a separate adhesive to provide strongeradhesion to the rotor blade.

In a specific but less preferred embodiment of this disclosure the tapecontains a patterned external surface of the adhesive bottom layer (3)as described above but a non-profiled, e.g. a planar top layer whereinthe non-profiled top layer is made of the materials as described above.In this less preferred embodiment the tape has no cross-sectionalprofile. In this particular embodiment the top layer preferably has athickness of more than 50 μm and less than 5,000 μm. The tape accordingto this embodiment may also contain an adhesive foam layer as describedabove. Such embodiments can be prepared by extrusion through ordinarily(non-profiled dies) and coated or laminated onto the adhesive layer.Tapes according to the embodiment may be applied and used as describedherein above and below for the profiled tapes.

Protective tapes (1) as provided herein having an adhesive layer (3)with a patterned external surface may be used in connection with one ormore liquid adhesives. The liquid adhesive may be curable, whichprovides a bond by curing it, for example by thermal curing, orirradiation curing as described above. The adhesive may also be asettable adhesive, which provides a bond by setting, for example ahot-melt adhesive or a solvent-based adhesive or a two component (2K)adhesive, which contains two reactive components which cross-link whencombined providing an adhesive, moisture curable adhesives which setupon exposure to ambient moisture or a combination of curable andsettable adhesives. The liquid adhesives may be painted or sprayed ontothe rotor blade. The liquid adhesives may be applied to the rotor blade,to the tape or both prior to attaching the tape to the rotor blade. Theliquid adhesive enters the grooves of the tape and is allowed to set oris cured to bond the tape to the rotor blade. The dimension of thegrooves and their spatial arrangement with respect to each other can beadapted to the type of liquid adhesive used for achieving maximumadhesion and most convenient application. Typically, the liquid adhesivehas a viscosity at the temperature at which it is applied, preferablyroom temperature (25° C.) of less than 18,000 mPas or less than 10,000mPas or less than 5,000 mPas, typically from 50 to 16,000 mPas. In thisembodiment, where the patterned tape is used with separate liquidadhesives, the adhesive used in the patterned adhesive layer (3) of thetape has a viscosity at room temperature (25° C.) that is equal orgreater than the viscosity of the liquid adhesive. Typically, theadhesive of the patterned adhesive layer (3) has a viscosity of at least2,000, or at least 10,000 or from about 18,000 to about 60,000 mPas orgreater that 60,000 mPas at room temperature.

The liquid adhesives may be of the same chemical class (e.g. acrylicbased adhesives) as the adhesive of the patterned adhesive layer (3) butmay have a different, preferably lower viscosity such that it flows intothe grooves of the patterned bottom. Also suitable are liquid adhesivesthat belong to a different chemical class than the adhesives used in thepatterned adhesive layer (3). In one embodiment the adhesive used in thepatterned layer comprises an acrylate containing adhesive and the liquidadhesive is selected from acrylate and/or urethane comprising adhesivesor from silicone adhesives or from epoxy-based adhesives.

The adhesive bottom layer (3) may also contain a pattern as describedabove on its internal surface facing the top layer if improvement of theadhesion between top layer (2) or intermediate layers (if present) andthe adhesive layer (3) is required.

The pattern on the adhesive bottom layer (3) may be generated by knownmethods. For example, the grooves in the adhesive layer of the presentdisclosure may be made as described in WO 98/29516, which isincorporated herein by reference. The topography may be created in theadhesive by any contacting technique, such as casting, coating orcompressing. The topography may be made by at least one of: (1) castingthe adhesive layer on a tool with an embossed pattern, (2) coating theadhesive layer onto a release liner with an embossed pattern, or (3)passing the adhesive layer through a nip roll to compress the adhesiveagainst a release liner with an embossed pattern. The adhesive may becross-linked to provide a permanent topography. The topography of thetool used to create the embossed pattern may be made using any knowntechnique, such as, for example, chemical etching, mechanical etching,laser ablation, photolithography, stereolithography, micromachining,knurling, cutting or scoring. The pattern may also be imparted to theadhesive layer by using an appropriately patterned release liner.

The adhesive bottom layer (3) may be a single adhesive layer which maybe patterned as described above or non-patterned or it may containmultiple adhesive layers of different adhesives or of adhesives of thesame chemical class of adhesives (e.g. acrylic based adhesives, urethaneadhesives, silicone adhesives, rubber adhesives and the like) but havingdifferent physical properties like, but not limited to adhesivestrength, tack, elasticity and/or viscosity.

Tape constructions containing several abutting layers can be prepared bypreparing films and laminating them to create a multi-layered tape. In aspecific embodiment the tape (1) contains at least two superimposedadhesive layers making up the adhesive bottom layer (3). Such layers maybe prepared, for example, by a wet-in-wet coating process. In thewet-in-wet coating process a first layer of a curable adhesive precursoris coated onto a substrate (e.g. a release liner). The coated substrateis then subjected to a second coating step where a second curableadhesive precursor is coated on top. The adhesive precursors aretypically liquids and are provided in substantially uncured form. Forexample, they may have a polymerization degree of less than 50% or lessthan 25% or even less than 10%. The curable adhesive precursors may havea viscosity which keeps them separated from each other for the time theyare in the coating unit prior to subjecting them to curing. The adhesiveprecursor layers are then cured. It is believed that interfacialdiffusion occurs between the adhesive layers leading to a strongerinterfacial adhesion upon curing such that the resulting multi-layerproduct is more resistant to delamination. This wet-in-wet coatingprocess can also be used for making profiled adhesive layers in whichcase the most downstream coating knife, i.e the coating knife that isarranged at the end of the coating line, has a recess in the shape ofthe desired profile of the final tape. The coating knives leave a gapbetween the substrate (and coated substrate respectively) and the lowerend of the coating knife through which the adhesive layers and in someembodiments also an extruded protective film will be fed. The size ofthe gap between the lower ends of the coating knifes and the substrateand the profile of the recess of the most downstream (or last) coatingknife determine the thickness and profile of the tape.

Therefore, the disclosure provides a process for making a profiled tape(1) having a profile as described above, the process comprises:

-   -   (i) providing a substrate (4);    -   (ii) providing in a coating chamber (6) a coating knife (300)        having a profiled recess (301) at its end facing the substrate        (4) and which forms a gap (401) between its profiled lower edge        (301) and the substrate (4)    -   (iii) moving the substrate (4) relative to the coating knife        (300) through the coating unit (downstream direction),    -   (iv) providing to the upstream side of the coating knife (300) a        curable adhesive precursor thereby coating an adhesive layer (3)        onto the substrate (4);    -   (v) providing an extruded polymeric film (2) to the upstream        side of the coating knife (300) and feeding the film (2)        simultaneously with the coated adhesive layer (3) through the        profiled recess (301) of the coating knife (300), wherein the        film (2) is positioned between the profiled recess (301) of the        coating knife (300) and the adhesive layer (3);    -   (vi) curing the adhesive of the multilayer tape thus obtained,        wherein the profile of the coating knife (300) and the size of        the gap (401) between the coating knife (300) and the substrate        (4) define the cross-sectional profile of the tape (1).

The process as described above may contain one or more further coatingknives arranged in front of the coating knife (300), i.e. in an upstreamposition with respect to knife (300), through which further adhesiveprecursors may be fed. The knives are arranged such that they leave agap between the substrate (4) and their lower edges for the adhesive ora coated layer to pass through. This way, multiple layers of adhesivesmay be formed. Such a process is referred to as a wet-in-wet processbecause the curable adhesive precursors are typically liquidcompositions. These coating knives may have a profiled recess at theirlower edge or may have a flat lower edge. For example a further coatingknife (200) may be positioned upstream to the coating knife (300) andleaving a gap between coating knife (200) and substrate (4). On theupstream side of the coating knife (200) a first adhesive precursor isfed around the edge of the coating knife (200) thereby coating a firstadhesive layer (7) onto the substrate (4) which is then fed through thecoating chamber (6) towards the downstream coating knife (300) describedabove. The gap of coating knife (300) is chosen such that the secondadhesive precursor introduced in chamber (6) and the protective liner(2) can be coated onto the layer already formed on the substrate to formthe multilayer tape (1). The coating knife (300) having the profiledrecess is the most downstream coating knife, i.e. it is positioned atthe end of the coating line before the tape reaches the curing unit.

The curable adhesive precursors used in this process may become adhesiveor fully adhesive only upon curing. The adhesives may be fed through thecoating knife under ambient pressure or an over-pressure, at roomtemperature or at increased temperatures, i.e. temperatures above roomtemperature. Preferably, the adhesive precursors are used in thisprocess, i.e. curable adhesives, more preferably UV-curable adhesives.Preferably, the adhesives have a degree of polymerization of less than50%, or less than 25% or less than 10%. Instead of one coating chamber,more than one coating chambers, preferably abutting each other, may beused.

The adhesives used to make the tape according to the above describedprocess may be of different chemical classes or of the same chemicalclass but of different physical properties. For example at least oneadhesive, preferably the one adjacent to the top layer (2), may be anadhesive foam material. It may contain solid or hollow particles, it maycontain expendable particles, in particular pentane filled expendablemicrospheres, gaseous cavities, or combinations thereof. The adhesivesand/or their precursors of the above described process typically haveviscosities that prevent them from quickly mixing which each other. Theadhesives and/or their precursors may have identical or differentviscosities. Typically, one adhesive and/or its precursor has aviscosity of at least 1,000 mPas at 25° C. and up to 30,000 mPas or upto 10,900 mPas at 25° C. and the other adhesive and/or its precursor,preferably being a foam adhesive, has the same viscosity or a viscosityof from about 2,000 to 12,000 mPas at 25° C., in particular from 2,500to 9,000 mPas at 25° C.

The substrate used in this process typically is a release liner but mayalso be an intermediate layer. The release liner may be structured toprovide a patterned adhesive bottom layer (3).

Release Liner

The adhesive bottom layer (3) may be covered on its external surface bya release liner (4) for convenient handling and storage. The releaseliner (4) may be structured on the side facing the adhesive to impart apattern as described above to the adhesive. The release liner (4) may beany release liner or transfer liner known to those skilled in the art.In case of providing a patterned external surface of the adhesive layerthe release liner may be embossed. Typical release liners includepolymer coated paper with a silicone release coating, a polyethylenecoated polyethylene terephalate (PET) film with silicone releasecoatings, or a cast polypropylene film with a silicone release coating.The release liner (4) typically has a thickness of between 50 and 500μm.

Application of the Tape

A typical rotor blade is shown in FIG. 6. As shown in FIG. 6 the blade(11) has a leading edge (12) and a trailing edge (11). The leading edgeof the rotor blade is the side that predominantly faces the wind. Thetape (1) may be applied to the rotor blade by removing the release linerand wrapping the tape around the rotor blade, typically around theleading edge of the rotor blade and bonding the tape to the blade. Thetape (1) is preferably attached to the blade such that it covers theleading edge with its thicker part and the thinner sides of the tapedirected towards the trailing edge of the blade.

In a particular embodiment of the present disclosure a tape (1) having apatterned bottom adhesive layer (3) as described above is provided. Aliquid adhesive as described above is provided and applied to the bladeon the parts to be covered by the tape (1) or on the adhesive side ofthe tape (1) or both. The tape (1) is then attached to the blade and theliquid adhesive is cured (UV-curing or thermal curing in case theadhesives is UV-curable or thermally curable), or the adhesive isallowed to set in case the liquid adhesive obtains its adhesive strengthby setting (e.g. by evaporation of solvent, moisture curing or reactioncuring in case of a 2K system). The tape (1) according to thisembodiment is attached to the blade by an adhesive bond formed betweenthe liquid adhesive and the patterned adhesive bottom layer (3) of theprotective tape (1).

The disclosure will now be described by way of examples and lists ofspecific embodiments for illustrative purposes only. It is not intendedto limit the disclosure to the examples and the specific embodiments.

List of Specific Embodiments

1. A multilayer protective tape (1) for rotor blades of wind energyturbines said tape (1) having a protective top layer (2) comprising apolymer film and an adhesive bottom layer (3), wherein the top layer (2)has a continuous surface (S) that is outwardly curved or outwardlytrapezoidal such that the tape (1) has a cross-sectional profile havingan inner section between two lateral sections and wherein the innersection has a thickness (Ti) made up by the thickness of the top layer(2) and adhesive bottom layer (3) that is greater than the thickness ofat least one of the lateral sections (T1, T2) made up by the thicknessof the top layer (2) and adhesive bottom layer (3) and wherein thethickness (T1 or T2) of at least one lateral section is at most 600 μmand the thickness of the inner section (Ti) is at least 330 μm.2. The tape (1) according to embodiment 1 wherein the inner sectioncomprises up to 90%, up to 95% or even up to 99% of the width of thetape.3. The tape (1) according to any one of the preceding embodiment whereinthe cross-sectional profile of the tape is symmetric.4. The tape (1) according to any one of the preceding embodimentswherein the adhesive bottom layer (3) has an upper surface facing thetop layer (2) and a bottom surface opposite thereto and wherein thebottom surface is patterned to comprise a plurality of grooves or dots.5. The tape (1) according to any one of the preceding embodimentswherein the adhesive bottom layer (3) comprises across its thickness atleast two adhesive layers of which one adhesive layer comprises a foamadhesive.6. The tape (1) according to embodiment 5 wherein the adhesive layer (3)is prepared by a wet-in-wet coating process.7. The tape (1) according to any one of the preceding embodimentswherein the top layer (2) has a uniform thickness.8. The tape (1) according to any one of the preceding embodimentswherein the top layer (2) is outwardly curved.9. The tape (1) according to any one of the preceding embodimentswherein the top layer (2) is outwardly convex.10. The tape (1) according to any one of embodiments 1 to 9 having athickness at its inner section (Ti) of from 400 μm up to 5,000 μm and athickness at the sections (T1, T2) of up to 350 μm.11. The tape (1) according to any one of the preceding embodimentswherein the adhesive layer (3) comprises an acrylic adhesive.12. The tape (1) according to any one of the preceding embodimentswherein the top layer (2) comprises a polyurethane.13. The tape (1) according to embodiment 1 or 2, wherein thecross-sectional profile is not symmetric.14. The tape (1) according to embodiment 13, wherein the thickness (T1,T2) at the lateral sections of the tape (1) is not equal.15. The tape (1) according to any one of the preceding embodiments 13 to14 wherein the adhesive bottom layer (3) has an upper surface facing thetop layer (2) and a bottom surface opposite thereto and wherein thebottom surface is patterned to comprise a plurality of grooves or dots.16. The tape (1) according to any one of the preceding embodiments 13 to15 wherein the adhesive bottom layer (3) comprises across its thicknessat least two adhesive layers of which one adhesive layer comprises afoam adhesive.17. The tape (1) according to embodiment 16 wherein the adhesive layer(3) is prepared by a wet-in-wet coating process.18. The tape (1) according to any one of the preceding embodiments 13 to17 wherein the top layer (2) has a uniform thickness.19. The tape (1) according to any one of the preceding embodiments 13 to18 wherein the top layer (2) is outwardly curved.20. The tape (1) according to any one of the preceding embodiments 13 to19 wherein the top layer (2) is outwardly convex.21. The tape (1) according to any one of embodiments 13 to 20 having athickness at its inner section (Ti) of from 400 μm up to 5,000 μm and athickness at one of it lateral sections (T1) of up to 350 μm.22. The tape (1) according to any one of the preceding embodiments 13 to21 wherein the adhesive layer (3) comprises an acrylic adhesive.23. The tape (1) according to any one of the preceding embodiments 13 to22 wherein the top layer (2) comprises a polyurethane.24. The tape (1) according to any one of the preceding embodiments 1 to7, and 10 to 12 having an outwardly trapezoidal cross-sectional profile.25. The tape (1) according to any one of the preceding embodiments 12 to18 and 21 to 23 having an outwardly trapezoidal cross-sectional profile.26. A multilayer protective tape (1) for rotor blades of wind energyturbines said tape (1) having a protective top layer (2) comprising apolymer film and an adhesive bottom layer (3), wherein the top layer (2)has a continuous surface, and wherein the adhesive bottom layer (3) hasan upper surface facing the top layer (2) and a bottom surface oppositethereto and wherein the bottom surface is patterned to comprise aplurality of grooves or dots, and wherein the tape has a thickness(combined thickness of layers (2) and (3) of more than 250 μm.27. The tape (1) according to embodiment 26 wherein the adhesive bottomlayer (3) comprises across its thickness at least two adhesive layers ofwhich one adhesive layer comprises a foam adhesive.28. The tape (1) according to embodiments 26 or 27 wherein the adhesivelayer (3) is prepared by a wet-in-wet coating process.29. The tape (1) according to any one of the preceding embodiments 26 to28 wherein the top layer (2) has a uniform thickness.30. The tape (1) according to any one of the preceding embodiments 26 to29 wherein the adhesive layer (3) comprises an acrylic adhesive.31. The tape (1) according to any one of the preceding embodiments 26 to30 wherein the top layer (2) comprises a polyurethane.32. The tape (1) according to any one of embodiments 26 to 31, whereinthe tape has cross-sectional profile that is not symmetric or issymmetric.33. The tape according to any one of embodiments 26 to 32, wherein thetape has a surface (S) that is outwardly curved or outwardly trapezoidalsuch that the tape (1) has a cross-sectional profile having an innersection between two lateral sections and wherein the inner section has athickness (Ti) made up by the thickness of the top layer (2) andadhesive bottom layer (3) that is greater than the thickness of at leastone of the lateral sections (T1, T2) made up by the thickness of the toplayer (2) and adhesive bottom layer (3) and wherein the thickness (T1 orT2) of at least one lateral section is at most 600 μm and the thicknessof the inner section (Ti) is at least 330 μm.34. The tape (1) according to embodiment 33 wherein the inner sectioncomprises up to 90%, up to 95% or even up to 99% of the width of thetape.35. The tape (1) according to any one of the preceding embodiments 33and 34 wherein the top layer (2) is outwardly convex.36. The tape (1) according to any one of embodiments 33 to 35 having athickness at its inner section (Ti) of from 400 μm up to 5,000 μm and athickness at the sections (T1, T2) of up to 350 μm.37. The tape (1) according to any one of embodiment 33 to 36 wherein thethickness (T1, T2) at the lateral sections of the tape (1) is equal ornot equal.38. The tape (1) according to any one of the preceding embodiments 26 to37 wherein the plurality of grooves or dots has a depth that is equal orless than equal than the thickness of the adhesive bottom layer (3).39. The tape (1) according to any one of embodiments 33 to 37 having athickness at its inner section (Ti) of from 400 μm up to 5,000 μm and athickness at one of it lateral sections (T1) of up to 350 μm.40. The tape (1) according to any one of the preceding embodiments 33 to39 having an outwardly trapezoidal cross-sectional profile.41. Use of a tape according to any one of embodiments 1 to 40 forprotecting a rotor blade of a wind turbine from erosion.42. Method of protecting a rotor blade of a wind turbine from erosioncomprising providing a protective tape (1) according to any one ofembodiments 1 to 40 and adhering it to the rotor blade.43. Method of protecting a rotor blade from erosion comprising

-   -   (i) providing a protective tape (1) according to any one of        embodiments 26 to 40;    -   (ii) applying a liquid adhesive to the rotor blade, to the        patterned bottom surface of the tape or both, and    -   (iii) attaching the tape to the rotor blade.        44. The method according to embodiment 43 wherein the liquid        adhesive has a viscosity of less than 20,000 mPas.        45. The method according to embodiment 43 wherein the liquid        adhesive has a viscosity of less than 20,000 mPas and the        adhesive of the patterned bottom layer has a viscosity of at        least 20,000 mPas.        46. The method according to embodiments 43 to 45 wherein the        liquid adhesive is sprayed onto the rotor blade.        47. A rotor blade comprising around its leading edge a        protective tape (1) according to any one of embodiments 1 to 40,        wherein the lateral sides of the tape face the trailing edge of        the blade.        48. Process of forming a multilayer tape (1) according to any        one of embodiments 1 to 40 comprising:    -   (i) providing a substrate (4);    -   (ii) providing in a coating chamber (6) a coating knife (300)        having a profiled recess (301) at its lower end facing the        substrate (4) and which forms a gap (401) normal to the surface        of the substrate (4);    -   (iii) moving the substrate (4) relative to the coating knive        (300) in a downstream direction;    -   (iv) providing to the upstream side of the coating knife (300) a        curable adhesive thereby coating an adhesive layer (3) onto the        substrate (4) through the gap (401);    -   (v) providing a polymer film (2) to the upstream side of the        coating knife (300) and feeding the film (2) simultaneously with        the adhesive layer (3) through the recess (301) of the coating        knife (300), wherein the film (2) is positioned between the        recess (301) and the adhesive layer (3);    -   (vi) curing the adhesive of the multilayer tape thus obtained,        wherein the profiled recess (301) of the coating knife (300) and        the size of the gap (400) between the coating knife (300) and        the substrate (4) define the cross-sectional profile of the tape        (1).        49. The process according to embodiment 48, wherein the        substrate (4) is a structured release liner.

Methods Viscosity:

The viscosity referred to in the general description of this disclosureand the viscosity of the materials used in the example section isBrookfield viscosity, measured at 25° C., unless specified otherwise.Measurements were carried out according to DIN EN ISO 2555:1999 at 25°C. using spindle 3, at 12 rpm in a Brookfield Digital Viscosimeter DV-IIcommercially available from Brookfield Engineering Laboratories, Inc.

Surface Roughness (Rz):

The surface roughness (Rz; average maximum height of surface profile)can be determined according to DIN EN ISO 4287 using the methodaccording to DIN EN ISO 4288.

Materials:

-   AA: Acrylic acid from BASF AG, Germany;-   2-EHA: 2-ethylhexylacrylate from BASF AG, Germany;-   IOA: Isooctyl acrylate, ester of isooctyl alcohol and acrylic acid,    from Sartomer Company, Cray Valley, France;-   HDDA: 1,6-Hexanedioldiacrylate (cross-linker) from Sartomer Company,    Cray Valley, France;-   Aerosil 972: fumed silica, filler, commercially available from    Evonik Industries GmbH, Germany;-   Glass bubbles K15: low density hollow glass microspheres (density    0.15 g/cm³), foam material, from 3M Company, USA;-   Omnirad BDK: 2,2-Dimethoxy-2-phenylacetophenone, UV-initiator, from    iGm resins, Waalwijk, Netherlands;-   Release liner: HOSTAPHAN 2 SLK, siliconized polyester, 75 μm    thickness from Mitsubishi, Wiesbaden, Germany.

EXAMPLES Preparation of Liquid Adhesive Precursor I:

The liquid adhesive precursor was prepared by combining 90% of ISO with10% AA and 0.04 pph (parts per hundred based on the sum of IOA and AA)of Omnirad BDK in a glass vessel under stirring for 30 minutes. Themixture was partially polymerized under a mitrogen-rich atmosphere by UVirradiation to a degree of polymerization of approximately 8% giving aBrookfield viscosity of approximately 3,000 mPas at 25° C. Subsequent tothe curing 0.12 pph of HDDA and 0.16 pph of Omnirad BDK were added andthe resulting mixture was thoroughly stirred for 30 minutes giving amaterial having a viscosity of 3,500 mPas.

Preparation of Liquid Adhesive Precursor II (Foam Adhesive):

The liquid precursor was prepared by combining 90% of 2-EHA with 10% AAand 0.04 pph (parts per hundred based on the sum of 2-EHA and AA) ofOmnirad BDK in a glass vessel under stirring for 30 minutes. The mixturewas partially polymerized under a mitrogen-rich atmosphere by UVirradiation to a degree of polymerization of approximately 8% giving aBrookfield viscosity of approximately 2,100 mPas at 25° C. Subsequent tothe curing 0.10 pph of HDDA, 0.16 pph of Omnirad BDK, 3 pph of fillerand 6 pph of Glasbubbles K15 were added and the resulting mixture wasthoroughly stirred for 30 minutes. The resulting precursor had aviscosity of about 10,000 mPas.

Example 1: Preparation of Protective Tape Having a Profiled Surface

A profiled adhesive layer was prepared by the wet-in-wet coating processin a coating station represented in FIG. 4 to which will now bereferred.

The coating unit (5) contained a coating chamber (6) made up by theupstream coating knife (200) at its front and the downstream coatingknife (300) at its back. The lateral walls of the coating station arenot shown. However, it is possible to provide more coating knives iffurther layers are to be prepared as described above. A substrate (4)was fed through the coating unit (5) in downstream direction asindicated by the straight arrow at a line speed of 6 m/min to reachfirst the upstream coating knife (200) and then the downstream coatingknife (300). A position facing the web direction (downstream direction)is referred to as “upstream position”. The position opposite to the“upstream position” is referred to as “downstream position”. Thesubstrate used in the example was a release liner (4). Both coatingknives were held in a position that left a gap (400),(401) between thelower ends of the coating knives (the ends facing the substrate) and thesubstrate (4). The upstream coating knife (200) had a flat lower end.The downstream coating knife (300) was provided at its lower end with aprofiled recess (301) having a trapezoidal shape as is shown in FIG. 5 A(viewed from the webdirection/downstream direction). The coating knives(200), (300) were arranged vertically spaced apart and heldindependently from each other. The liquid adhesive precursor (I) was fedon a rolling bead in front of coating knife (200) (upstream side of thecoating knife (200), onto the substrate and passed through the gap (400)between the lower end of the coating knife (200) and the substrate (4)thus coating the substrate to form a layer (7). The coated substrate wasfed into the coating chamber (6) where the second liquid adhesiveprecursor (II) was introduced onto to coated substrate (4) under ambientpressure forming a layer (8) superimposed on layer (7).

In the coating chamber (6), a solid film (2) in the form of a TPU linerof 150 μm thickness was conveyed on the upstream side of the coatingknife (300) and fed around the profiled recess (301) of the coatingknife (300) simultaneously with the liquid precursor II thus forming amulti-layer tape (1) containing an adhesive layer (3) having separateadhesive layers (7) and (8). The gap (400) between the first (upstream)coating knife (200) and the substrate (4) was such that the adhesivelayer (7) had a thickness of about 75 μm.

The gap (401) between the flat parts of the profiled recess of the loweredge of the coating knife (300) and the coated substrate (4) was about400 μm and the gap between the middle of the profiled recess and thesubstrate was about 1,200 μm. The resulting multilayer tape was thencontinuously cured in a 3 meter UV-curing station (2.07 mW/cm² duringthe first 2 m and 4.27 mW/cm² at the last meter) to yield an erosionprotection tape (1) having a profiled thickness. The cross-sectionalprofile of the resulting tape is shown in FIG. 5B. The solid lineindicates the thickness profile of the tape (including the top layer(2), adhesive layer (3) made up of layers (7) and (8) and the releaseliner (4). The dotted line indicates the profile of the profiledadhesive bottom layer (3)—without the top layer (2).

Example 1 is provided to demonstrate the construction of a complex tapehaving an outwardly curved profile with a uniform polyurethane film astop layer and an adhesive bottom layer containing several distinctadhesive layers. It is understood that also much simpler tapeconstructions are encompassed by the present disclosure. For, example,it may be sufficient to provide an adhesive bottom layer (3) containingjust one adhesive layer. Such less complex tapes can also be prepared inthe coating system as described above but then only the profiled coatingknife may be needed. The adhesive should be chosen such that itsviscosity and adhesive strength allows the tape to maintain its shape.Instead of using a foam adhesive also plain adhesives with no foam-typeproperties may be used. More complex tape constructions could also beprovided. In this case further coating knives may be added forgenerating additional layers.

The complex tape construction provided in example 1 allows for tapesbeing prepared having adhesive components fine-tuned to the desiredneeds for a protective wind tape. In particular it is believed that oneor more adhesive foam layers may add further protection to damagethrough sand or hailstones by providing elasticity to the tape.

Example 2 (Hypothetical): Protective Profiled Tape with PatternedAdhesive Layer

The tape prepared in example 1 can be adhered to a tape containing astructured adhesive layer. Such tapes are commercially available, forexample under the trade designation CONTROLAC 180 from 3M Company, St.Paul, USA. Such tapes contain a PVC top layer and a bottom layercontaining a structured adhesive. The profiled tape can be adhered withits adhesive bottom layer to the PVC side of the CONTROLTAC tape givinga protective tape having a structured adhesive layer at its bottom andan intermediate non adhesive layer (the PVC layer).

For making tapes without the intermediate layers that would result fromthe hypothetical example above, the adhesive layer of the multi-layertape prepared in example 1 can be provided with a pattern by the methodsdescribed in the description, for example, but not limited to, embossingusing a patterned release liner.

Example 3: Adhesion of a Tape with a Patterned Adhesive Bottom Layer toLiquid Adhesives

A protective tape having a patterned adhesive layer was prepared asfollows:

A PVC film having a patterned adhesive layer (CONTROLTAC 180 from 3MCompany, St. Paul, USA) was adhered to the adhesive side of a protectivefilm comprising a polyurethane resin as protective layer and an adhesivebottom layer (WINDTAPE 8607 from 3M Company). The protective tape had auniform profile but the experiment is provided to demonstrate theinteraction of the patterned adhesive layer with a liquid adhesive onbonding to rotor blades.

Three different adhesives of different viscosities where applied to thepatterned part of the protective tape, which was then wrapped around theleading edge of a glass fiber composite rotor blade and attached by handwiping from the middle to the sides to remove air and excess liquidadhesive. The liquid adhesive was allowed to cure according to thesupplier's instructions.

The following liquid adhesives were used:

-   Resin I: SCOTCH-WELD UV 11 from 3M Company, St. Paul, USA    (urethane-acrylate-based adhesive), viscosity 90 m Pas, UV curable    adhesive.-   Resin II: SCOTCH-WELD DP 600 SL polyurethane-based adhesive,    viscosity 2500-4050 mPas. 2K (2 component) adhesive which cures upon    combination of the two reactive components after 24 hours.-   Resin III: SCOTCH-WELD DP 810, acrylate-based adhesive, viscosity    20,000-40,000 mPas, UV curable adhesive.

The tapes using liquid adhesives I and II could be easily applied,repositioned and strongly bonded to the blade. Tapes with resin IIIcould not be easily attached to the blade.

To test the strength of the bond, the tapes were removed by hand fromthe glass-fiber composite. The test was compared by using a TPU-tapehaving a PSA layer at its bottom that was flat, i.e. not patterned. Thetape was attached to the same glass composite material. The tape wasremoved from the blade by hand which could be carried out more easilythan the tests done with adhesives I and II using the patterned materialas described above.

What is claimed is:
 1. A multilayer protective tape for rotor blades ofwind energy turbines said tape comprising: a protective top layercomprising a polymer film, and an adhesive bottom layer, wherein the toplayer has a continuous surface (S) that is outwardly curved or outwardlytrapezoidal such that the tape has a cross-sectional profile having aninner section between a first edge lateral section and a second edgelateral section, wherein the inner section comprises up to 30% of thewidth of the tape, and wherein the inner section has a thickness (Ti),the thickness of the first edge lateral section is T1, and the thicknessof the second edge lateral section is T2, wherein Ti is greater thaneach of T1 or T2, and wherein the thickness (T1 or T2) of at least oneedged lateral section is at most 600 μm and the thickness of the innersection (Ti) is at least 330 μm.
 2. The tape according to claim 1wherein the inner section comprises up to 50% of the width of the tape.3. The tape according to claim 1 wherein the inner section comprises upto 90% of the width of the tape.
 4. The tape according to claim 1,wherein the cross-sectional profile of the tape is symmetric
 5. The tapeaccording to claim 1, wherein the maximum thickness is at the middle ofthe tape across the width of the tape.
 6. The tape according to claim 1,wherein the cross-sectional profile of the tape is non-symmetric whereinthe thickness T1 may be greater than the thickness T2.
 7. The tapeaccording to claim 6, wherein the cross-sectional profile of the tape isnon-symmetric and wherein the maximum thickness is at the middle of thetape across the width of the tape.
 8. The tape according to claim 1,wherein the cross-sectional profile of the tape is non-symmetric andwherein the maximum thickness is offset from the middle of the tapeacross the width of the tape.
 9. The tape according to claim 1, whereinthe adhesive bottom layer has an upper surface facing the top layer anda bottom surface opposite thereto and wherein the bottom surface ispatterned to comprise a plurality of grooves or dots.
 10. The tapeaccording to claim 1, wherein the adhesive bottom layer comprises acrossits thickness at least two adhesive layers.
 11. The tape according toclaim 1, wherein the adhesive layer comprises one of an acrylicadhesive, a polyurethane adhesive or a polyurethane acrylate adhesive.12. The tape according to claim 1, wherein the top layer comprises apolyurethane.
 13. The tape according to claim 1, further comprising anintermediate layer between protective top layer and the adhesive bottomlayer.
 14. A rotor blade of a wind turbine protected from erosion, therotor blade comprising: a leading edge that predominantly faces thewind; a trailing edge opposite the leading edge; and a protective toplayer covering and bonded to the leading edge of the rotor blade by anadhesive bottom layer, wherein the top layer has a continuous surface(S) that is outwardly curved or outwardly trapezoidal, wherein theprotective top layer and the adhesive bottom layer have across-sectional profile having an inner section between a first edgelateral section and a second edge lateral section, wherein the innersection comprises up to 90% of the width of the top protective layer,and wherein the inner section has a thickness (Ti), the thickness of thefirst edge lateral section is T1, and the thickness of the second edgelateral section is T2, wherein Ti is greater than each of T1 or T2, andwherein the thickness (T1 or T2) of at least one edged lateral sectionis at most 600 μm and the thickness of the inner section (Ti) is atleast 330 μm.
 15. The rotor blade of claim 14, wherein the inner sectionis disposed over the leading edge and the first and second edge lateralsections extend toward the trailing edge of the blade.
 16. Method ofprotecting a rotor blade of a wind turbine from erosion comprising (i)providing a protective tape, wherein the protective tape comprises aprotective polymer film top layer and an adhesive bottom layer having anupper surface facing the top layer and a bottom surface oppositethereto, wherein the bottom surface is patterned to comprise a pluralityof grooves or dots, wherein the tape has a cross-sectional profilecomprising an inner section having a thickness Ti between a first edgelateral section and a second edge lateral section, wherein the thicknessof the first edge lateral section is T1, and the thickness of the secondedge lateral section is T2, wherein Ti is greater than each of T1 or T2,wherein the thickness (T1 or T2) of at least one edge lateral section isat most 600 μm and the thickness of the inner section (Ti) is at least330 μm, (ii) applying a liquid adhesive to the rotor blade, to thepatterned bottom surface of the tape or both, and (iii) attaching thetape to a leading edge of the rotor blade such that the edge lateralsections of the tape face a trailing edge of the blade.
 17. The methodaccording to claim 16, wherein the liquid adhesive has a viscosity ofless than 20,000 mPas.
 18. The method according to claim 16, wherein theliquid adhesive is sprayed onto the rotor blade.
 19. The methodaccording to claim 16, further comprising the step of curing the liquidadhesive.
 20. The method according to claim 16, wherein the liquidadhesive is selected from acrylate and/or urethane containing adhesives,silicone adhesives and epoxy-based adhesives.